Bath put in place and sealant put in but two sides keep cracking everytime the bath is run, tear out the sealant do it again and it just keeps cracking. I'm cobcerned about water seeping down the cracks and causing water damage. Can someone please advise what I should be doing so this doesn't happen, plumber done the original job but just doesn't want to know,
When was the bath installed? I suspect recently from the way you speak. Can you confirm?.
If I'm right then you do nothing apart from deal with the "plumber doesn't want to know" issue as he needs to come back and fix it. If he won't do it on your invitation then I'd go to trading standards.
If the installation is a long time ago then it's maybe a different issue and you need to provide more detailed information.
Is it a steel bath or a plastic one? In either case Alda is right the bath must be securely mounted. I wouldn't use bags of sand though to load the bath - never get even load distribution.
The plumber should have known that he should have filled the bath to about 3/4 full before applying sealant. Then the sealant is applied and left for 24 hours to cure before pulling out the plug. The sealant never sets and will expand and contract as the bath is used.
This process of filling the bath results in the sealant being in compression when the bath is empty and it, therefore, shouldn't crack when the bath is full. If sealant is applied when the bath is empty then as it fills it sinks the sealant is constantly under tension and eventually cracks.
If you have already tried to solve the problem yourself then your plumber can easily walk away from his obligations on the grounds that someone has interfered with his work and he could reasonably charge you to fix it. If it's as he left it then IMHO he should sort it ot for you at no cost to you.
Sorry to be late answering this one as I don't like resurrecting old threads in general.